Self-locking folding box



Dec. 25, 1951 Filed Dec. 4, 1947 R. B. MELLER SELF-LOCKING FOLDING BOX 2 SHEETS-SHEET l Fig. 3/!

IN V EN TOR. Regina/0 B. Me//er Ma W A 77' ORNE Y Patented Dec. 25,1953

IUNITQED SELF-LOCKING FOLDING Box: Reginald Beavis Heller, Oakland, Calif., assignor to Demise-Jason Company,

California a corporation of Application December 4, 1947, Serial No. 789,739 4 Claims. (01. 229-35) The invention provides, among other features,

an improved interlock for rigidly connecting together overlapping portions of a box blank, it provides an improved box blank which may be completely assembled on automatic high-speed box machinery of relatively simple construction and it provides a box which, after assembly, has the strength and rigidity of a glued box.

The practice of interlocking and securing together panels of a box blank without the aid of adhesive or other securing means is basically not new. However, conventional forms of interlock are relatively weak and usually do not result in a very rigid box structure. This is the principal reason why interlocks of the glueless type are commonly limited to boxes where strength is of secondary importance.

The present invention provides an improved type of interlock which, as regards strength and rigidity, is comparable to a glued connection and which extends the use of glueless interlocks to a large field of boxes which heretofore was closed to conventional glueless interlocks because of their inherent limitations.

Relatively great strength is obtained in the novel interlocks embodying the present invention by an improved form of engagement between the portions of the box blank to be'interconnected employing a cut edge on one blank portion to interengage a cut edge on another blank portion so that an edge-to-edge interlock of substantial length results, as distinguished from the conventional hook lock in which the engagement is of a point-to-point type.

Forces sustained by the interlock embodying the invention lie substantially in the plane of the interlocked panels, that is, in a direction in which the board offers greatest resistance to deformation. The forces are distributed over a considerable extent of abutting cut edges whereby deformation of the interengaging portions of the box blank is avoided.

The invention utilizes the inherent resiliency of the box board for automatically moving the interlocking edges into engagement when the blank is folded and maintaining them engaged.

The invention provides a form of interlock which is aided by, but is not dependent on, the resiliency of the board for maintaining the interlock intact andis secured against accidental disengagement by special safety means. This particular feature makes the invention admirably suited for the making of self-locking boxes from low grades 'of board such as chip board which heretofore was not safe to use because of its low resiliency.

The novel interlock is particularly suited for securing together box panels at a box comer. However, the invention is not limited to such an application, but may advantageously be employed wherever it is desired to interlock two panels of a folding box in overlapping relationship to prevent movement of one panel relatively to the other about a hinge axis extending at an angle with respect to the surface of the panel.

interlocks embodying the present invention are particularly strong in that the board is not subjected to tearing as in the case of the conventional hook look, but is subjected to compression, the forces of compression acting in a direction in which the board offers greatest resistance. This is an important advantage which makes the invention particularly valuable for boxes subjected to moisture which, as is well known, reduces the tear strength of paperboard considerably.

The various objects, features and advantages of the invention will apear more fully from tne detailed description which follows accompanied by drawings showing, for the purpose of illustration, a preferred embodiment and application of the invention.

The invention also consists in new and improved details of construction hereinafter set forth and claimed.

\ Although the characteristic features of this invention which are believed to be novel will be particularly pointed out in the claims appended hereto, the invention itself, its objects and advantages, and the manner in which it may be carried out may be better understood by referring to the following description taken in connection with the accompanying drawings forming a part of it in which:

Figure 1 is a plan view of a flat box blank embodying the invention, the inside surface of the blank facing the observer;

- Figure 2 is a plan view of the blank shown in .2, at a furtherndvanced stage of assembly short-' ly prior to the formation of interlocks .at the four corners of the box;

Figure 3a is, a fragmentary view illustrating an alternative way of flexing certain panels and panel portions in forming the interlock;

Figure 4 is an outside view, on an enlarged scale, of a corner portion of the box, the box panels being shown in locked position prior to the performance of a final step insecuring the .15

panels against accidental disengagement;

Figure 5 is an inside view, partly in section, of

the comer portion shown in Figure 4;

Figure 6 is an outside view of the corner portion after performance of the final assembly step for securing the interlock against accidental disassembly;

Figure '7 is an inside view, partly in section, of the comer portion shown in Figure 6; and

Figure 8 is a plan view of the completed box; and

Figure 9 is a side view of the completed box.

In the following description and in the claims, various structural details will be identified by specific names forconvenience. The names, howso ever, are intended to be as generic in their application as the art will permit. Corresponding reference characters refer to corresponding parts' in the several figures of the drawings. I

In the drawings accompanying, and forming part of, this specification, certain specific disclosure of the invention is made for the purpose of explanation of broader aspects of the invention, but it is understood that the details may be modified in various respects without departure from the principles of the invention and that V the invention may be applied to other structures than the ones shown.

The blank A shown in Figure 1 is substantially rectangular in outline, resulting in a minimum waste of material in cutting the blank from stock of larger size. The blanks may be cut and scored in multiple, from a large sheet or roll of paperboard or other suitable foldable material on an automatic cutting and scoring machine. Only one side of the blank need be decorativcly finished or imprinted, since only one side of the blank appears as the outside of the finished box. The blank A is subdivided by several scored fold lines to provide a bottom panel II to which side wall panels I2 and I3 are hinged along side fold lines I4 and I5. End panels I6 and II are hingedly connected to the bottom panel II along end fold lines I8 and I9, respectively. Lock panels 20 and 2I are hingedly connected to the 0 end panel I5 along fold lines 22 and 23, respectively. The fold lines 22 and 23 are either aligned with, or parallel and slightly offset with respect to, the side fold lines I4 and I5 to compensate for the thickness of the board in the succeeding folding operations, as is customary in the art. Lock panels 24 and 25 are hingedly connected to the end panel I1 along fold lines 26 and 21 in a similar manner as just described. The lock panels20, 2|, 24 and 25 are separated from the side panels I2 and I3 by cuts-28, 29, 30 and 3i, respectively, each of the cuts extending to the intersections of fold lines I4 and I5 with the fold lines l3 and I3.

According to the present invention, glueless interlocks are provided for the several panels.

These interlocks comprise internal cut lines 32, I2 and I3, whereby internal tongues 36, 31, 33.- and 33 are- 33, 34 and 35, in the side panels formed in the panels, each tongue being resiliently defiectable with respect to the remainder of r such that portions of the cut edges formed thereby will, upon assembly of the blank into box form, move into alignment with portions ofthe lntemal cuts 32, 33, 34 and 35 so that an edgeto-edge engagement results therebetween as will hereinafter become apparent. Lock tabs 48,43, 50 and 5I are bordered by the external cuts 44, 45, 46 and 41. The lock tabs extend beyond the confines of the internal tongues.36, 31,33 and 33, respectively when the lock flaps 20, 2!, 24 and 25 are folded face to face with the side walls I2 and I3 to form box corners. The internal cuts 32,33, 34 and 35 comprise certain portions 52, 53, 54 and 55 beyond which the lock tabs 48, 50, 49 and 5I, respectively, extend as is particularly apparent from Figures 4 and 5. The purpose of this arrangement will become apparent from a consideration of the assembly procedure of the blank A which may be as folows:

The side panels I2 and I3 are first folded about their respective side fold lines I4 and I5 into substantially upright position with respect to the bottom panel II, as shown in Figure 2. The end panels I6 and I! are also folded about their respective folcLlines I3 and I9 towards their ultimate upright position, and substantially simultaneously the lock panels 20 and 2| and the lock panels 24 and 25 are folded with respect to the end panels I6 and H to which they are hinged along the fold lines 22,23 and 26, 21, respectively,

until they lie face to face with the side wall panels with respect to the remainder of the wall panels I2 and I3 in which they are formed as illustrated in Figure 3, or the end portion of the wall panels I2 and I3 are flexed with respect to the internal tongue, as shown in Figure 3a, whereby wedgeshaped spaces are formed between the internal tongues and the side wall panels into which the lock panels 20, 2|, 24 and 25 may be moved. In

the illustrated form of box, this involves swinging movement of the lock panels 20, '2I, 24 and 25, together with the end wall panels I6 and I1 about the fold lines I8 and I3 as a hinge axis, so

that the lock panels 20, 2|, 24 and 25 enter the wedge-shaped spaces bottom edge first, the bottom edge being formed by the cuts 28, 29, 30 and 3|.

As soon as the lock panels have entered the -wedge-shaped spaces formed by the internal tongues 36, 31, 38 and 39 and the remainder of the side wall panels I2 and I3, the internal tongues are released permitting the tongues, by reason of the resiliency inherent in the board, to return toward the planes of the respective side wall panels in which they are formed.

The resiliency causes the internal tongues to bear down upon the respective lock panels. When the end panels I6 and I! reach a position upright with respect to the bottom panel I I, the external cuts 44, 45, 46 and 41 move into alignment In order to secure the interlocks against accidental disengagement, the lock tabs 48, 49, 50

and are forced from the position in which they overlie the sidewall panels I2 and I3 as indicated in Figures 4 and 5 through the internal cuts 32, 33, 34 and 35 past the edges 52, 53, 54

and 55 into a position in which they underlie the Y side wall panels as indicated in Figures 6 and '7. This is "conveniently accomplished by grasping the lock panel 25 near the point P with a suitable tool and pulling it towards the inside of the box as indicated in Figure '5. In this position, the lock tabs 48, 49, 50 and 5| positively maintain portions of the lock panel 20, 2|, 24 and 25 deflected into the plane of the side wall panels l2 and I3, whereby an edge-to-edge engagement between the side walls and the lock panels is securely maintained. The size of the lock tabs 48, 49, 50 and 5| is preferably so selected that they can be flexed past the edges 52, 53, 54 and 55 without breaking or creasing so that their stiffness remains unimpaired.

In interengaged position, the cut edges are so disposed that the one end of the internal cut lies to one side of the portion of interlock, and the end of the interengaged external cut closest to the body of the other panel lies on the other side of the portion of interlock. This particular disposition of the cuts results in deflection of portions of the side wall panel as well as portions of the lock panels by reason of the resiliency of the stock. 1

,/,Referring briefly to Figure 1, it is easily apparent that the internal tongue 38 will exert least resistance to a force tending to deflect it with respect to the remainder of the side wall 13 if the force is applied near the tip of the tongue 38 than if it were applied near the root of the tongue, that is, near the ends of the cut 34. Similarly, it is quite apparent that the two portions of the lock panel 21 lying to either side of the external cut 45 are more easily deflected by a force applied near the lock tab 49 than if the same force were applied near the inner end of the cut 45 where the cut ends in the body of the panelZ I.

The interlock produced according to the pres- .ent invention has the peculiar feature that the portion of the internal tongue near the tip of the tongue, where it is most easily deflected, lies next to a portion of the lock panel adjacent the inner end of the out where the portions of the lock panel offer much resistance to deflection. More particularly, the portion of the internal tongue 38 near the top of the tongue where it is most easily deflected lies next to a portion of the lock panel 2| adjacent the inner end of the 4 cut 45 where the portions of the lock panel offer much resistance to deflection. Similarly, the root of the tongue 38 lies adjacent to the end portion 49 of the lock panel 2|, where the lock panel is most easily deflected.

In interlocked position, each lock panel overlies the respective side wall panel but is threaded through the respective internal cut and therefore underlies partly the internal tongue formed by the internal cut. This causes portions of the lock panels 20, 2|, 24 and 25 to be deflected into the plane of the respective side wall panels I2 and 13, whereby a full edge-to-edge engagement is produced between the side walls and the lock panels.

The inherent resiliency of the stock is utilized causing cut edges of the side wall panels to snap The invention is adapted to boxes designed for into engagement with cut edges on the lock panel, and the resiliency of the stock is further utilized in maintaining the edges in engagement. The respective lock tabs 48, 49, 50 and Si provide additional safety.

The resultant interlock is positive, substantially free from play or lost motion, it is extremely resistant to reopening caused by pressure of the box contents bearings against its side and end walls. Pressure of contents against the box walls merely results in increased edge-to-edge pressure along the portion of interlock in a direction in which the boardis most resistant to force. This characteristic makes the interlock produced according to this invention comparable in strength to a glued connection.

It is quite evident, however, that the novel interlock can be formed more rapidly than a glued connection because it is not necessary to maintain portions of the folded box under pressure for a certain length of time as in the case of a glued box where time is required in order to permit the glue to set.

The invention thus provides a convenient, inexpensive and secure interlock between carton panels which, with respect to rigidity and reliability, is comparable to a glued connection. The interlock is formed solely by the board itself from which the box is formed, advantage being taken of the stiffness and the resiliency of the board in forming and maintaining the interlock.

' before been supplied.

Obviously the present invention is not restricted to the specific forms of blanks illustrated and described. nor is it restricted to the specific steps or the sequence of steps disclosed.

Whereas the present invention has been explainedby reference to boxes in which the wall panels form ninety degree angles with respect to one another, it is quite apparent that the invention may also be applied to the manufacture of boxes in which the angle between panels is greater or less than ninety degrees. Also, it is obvious that instead of providing the end panel of a box with a lock panel which is intcrlocked with a sidewall, the lock panel may be hinged to the side wall and locked to the end wall or quite generally be hinged to any wall and locked to another wall which lies face to face with the lock panel. Such applications are evident to persons skilled in the art after becoming acquainted with the principles of the present invention.

Thus, various additions, omissions, modifications, substitutions and other changes may be made without departing from the spirit and from the essence of this invention.

What is claimed is:

1. A folding box made from a sheet of foldable stock and comprising, a main panel, a first corner when the panels are in corner forming wall panel hingedly connected to said main panel along a first fold line, a second wall panel of one of said wall panels and foldable into a position parallel with the other wallpanel when said panels are in corner forming position, and an interlock between said lock flap and said other wall panel, the interlock comprising, an internal out o! bent outline in said other wall panel forming an internal resilient tongue in said other 'wall panel pointing towards the box position, said intemal' cut comprising an upwardly sloping cut portion terminating in a terminal out extending at an angle with regard to said upwardly sloping cut, the internal tongue, upon flexing with respect to the remainder of said other wall panel, forming awedgeshaped opening in said other wall panel into which said flap may be swung, said flap having an external cut extending into it from an outer edge, said external cut coinciding in interlocking position with said upwardly sloping cut in lineg-to-line, as distinguished from point-to-point coincidence, said external cut forming an external tongue on said flap, the tip of said external tongue being bordered by said external cut and at least extending'at an angle with regard to saidupwardly sloping cut, the internal tongue. p n flexing with respect to the remainderofsaid other wall panel, iorming a wedge-shaped opening in said other wall panel into which said flap may be swung, said nap having an external cut ,extending into it from an outer edge, said external cut coinciding ,in interlocking P sition with said upwardly sloping cut in-line-to-line. as distinguished from point-to-point coincidence,

said external cut forming an external tongue on said flap, said external tongue being bordered by said external cut and at least one outer edge one outer edge of said flap, the distance from o the tip of the external tongue to the point of intersection of said fold lines being less than the distance from said point of intersection to the end of said internal cut farthest from the fold line of said other panel but greater than the distance from said point to the point of intersection of said upwardly sloping cut and said terminal cut. whereby said flap is insertable into said wedge-shaped opening by a swinging motion of said one panel about its fold line, so that said external tongue comes to lie underneath said internal tongue, and said tip extending beyond the confines of said internal tongue and across said terminal cut to'overiie a portion of said remainder of the other wall panel, said tip being for folding ,boxes for assembling, in corner forming relationship, a main panel, two wall panels hinged to the main panel along fold lines forming an angle; and a flap hinged to the side edge of one of the wall panels, the flap being foldable into a position parallel with the other wall panel when the panels are in comer forming position, the other wall panel having a out side edge at the comer forming an anglewith the fold line of said other panel equal to the angle which said one panel forms with the main panel in the assembled comer, the corner construction being characterized by an interlock comprising an internal cut of bent'outline in said other wall panel forming an internal resilient tongue in said other wall panel pointing towards the box corner when the panels are in corner forming position, said internal cut comprising an upwardly sloping cut terminating in a terminal cut of said flap, the distance fromthe tip of the external tongue to the pointof intersection of said fold lines being less than the distance from I said point of intersection to the end of said inremainder of the other wall panel, said tip being forceable against the resistance of the stock from Y which it is formed, from an overlying position with respect to said other panel past said terminal cut into an underlying position, thereby providing a safety catch maintaining the respective interlocking edges in edge-to-edge engagement.

3. A folding box made from a sheet of foldable stock and comprising, a main panel, a first wall panel hingedly connected to said main panel along a first fold line, a second wall panel hingedly connected to said main panel along a second fold line intersecting said first fold line at an angle, said panels being foldable about said fold lines with respect to one another into a position in which they form a box corner, a lock flap hingedly connected to the side edge of one of said wall panels and foldable into a position parallel with the other wall panel when said panels are in corner forming position, and an interlock between said lock flap and said other wall panel, the interlock comprising, an internal cut of bent outline in said other wall panel forming an internal resilient tongue in said other wallpanel pointing towards the box cornervwhen the panels are in comer forming position, said internal cut comprising an upwardly sloping out terminating in a terminal cut substantially parallel to the hinge line of said other wall panel, the internal tongue, upon flexing with respect to the remainder of said other wall panel, forming a wedge-shaped opening in said other wall panel into which said flap may be swung, said flap havingan external tongue thereon oppositely directed, in interlocking position, to said line of said other panel, but greater than the distance from said point to the point of intersection of said upwardly sloping cut and said terminal cut, whereby said flap is insertable into -said wedge-shaped opening by a swinging motion of said one panel about its fold line, so that said external tongue comes to lie underneath said internal tongue, and said tip extending beyond the confines of the internal tongue and across said internal cut to overlie a portion of said remainder of said other wall panel, said tip being forceable against the resistance of the stock from which it is formed, from an overlying position with respect to said other panel past said terminal cut into an underlying position, whereby a safety catch is provided maintaining the. respective interlocking edges in edgeto-edge engagement.

4. A-folding box made from a sheet of foldable stock and comprising, a main panel, a first wall panel hingedly connected to said main panel along a first fold line, a second wall panel hingedly connected to said main panel along a second fold line intersecting said first fold line at an angle, said panels being foldable about said fold lines with respect to one another into a position in which they form a box corner, a lock flap hingedly connected to the side edge of one of said wall panels and foldable into a position parallel with the other wall panel when said panels are in corner forming position, and an interlock between said lock flap and said other wall panel, the interlock comprising, an internal cut of bent outline in said other wall panel forming an internal resilient tongue in said other wall panel pointing towards the box corner when the panels are in corner forming position, said internal cut comprising an upwardly sloping cut terminating in a terminal cut substantially parallel to the hinge line of said other wall panel, the internal tongue, upon flexing with respect to the remainder of said other wall panel, forming a wedge-shaped opening in said other wall panel into which said flap may be swung, said flap having an external tongue thereon oppositely directed, in interlocking position, to said internal tongue, said external tongue being bordered by two external cut edges forming an angle and meeting at the tip of said external tongue, one of said external cut edges coinciding in interlocking position with said upwardly sloping portion of said internal cut in line-toline, as distinguished from point-to-point coincidence, the distance from the tip of the external tongue to the point of intersection of said fold lines being less than the distance from said point of intersection to the end of said internal cut farthest from the fold line of said other panel, but greater than the distance from said point to the point of intersection of said upwardly sloping cut and said terminal cut, whereby said flap is insertable into said wedge-shaped opening by a swinging motion of said one panel about its fold line, so that said external tongue comes to lie underneath said internal tongue, the engaging cut edge of the external tongue being a substantially straight edge extending to said tip, said tip being forceable against the resistance of the stock from which it is formed, from an overlying position with respect to said other wall panel through said internal cut and past said end portion into an underlying position, thereby providing a safety catch maintaining the respective interlocking edges in edge-to-edge engagement.

REGINALD BEAVIS MELLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 399,891 Harley Mar. 19, 1889 691,458 Ferres Jan. 21, 1902 756,478 Davidson Apr. 5, 1904 2,004,098 Andrews June 11, 1935 2,193,925 Huye Mar. 19, 1940 2,303,796 Rueckert Dec. 1, 1942 2,475,279 Dunning July 5, 1949 2,528,900 Meller Nov. 7, 1950 2,550,582 Meller Apr. 24, 1951 

